THE MECHANISM OF DIGESTION. 103 



Around the extremity of the rectum is a band of smooth mus- 



FIG. 45. 



Diagram of Alimentary Tract. Angles of mouth slit to show the back 

 of the buccal cavity and the top of the pharynx. (c) Cardiac, (p) Pyloric 

 parts of stomach ; (d) Duodenum; (i) Jejunum and Ilium; (oc) Ascend- 

 ing, (tc) Transverse, and (dc) Descending Colon ; (r) Rectum ; (a) Anus. 



cle, which remains in a condition of persistent or tonic contraction. 



